Currently we do not have the j2 template for seraph-config.xml. Confluence image on the other hand, has it. Due to this, it is not possible to include a modified seraph-config.xml via j2 templates alongside other templates as well under $JIRA_INSTALL_DIR/etc.

Overwriting the j2 template is the official, supported way to supply a custom file to an image.

Workaround

Create a custom Docker build from the base https://hub.docker.com/r/atlassian/jira-software image, and COPY the modified seraph-config.xml to opt/atlassian/jira/atlassian-jira/WEB-INF/classes/seraph-config.xml.

Example Dockerfile:

FROM atlassian/jira-software:8.8.0
COPY seraph-config.xml.modified /opt/atlassian/jira/atlassian-jira/WEB-INF/classes/seraph-config.xml